Oxalyl chloride

Oxalyl chloride is a chemical compound with the formula (COCl)₂. This colourless, sharp-smelling liquid, the diacyl chloride of oxalic acid, is a useful reagent in organic synthesis.[3]

Oxalyl chloride

Names
Preferred IUPAC name Oxalyl dichloride[1]
Systematic IUPAC name Ethanedioyl dichloride[1]
Other names Oxalic acid chloride Oxalic acid dichloride Oxalic dichloride Oxaloyl chloride
Identifiers
CAS Number	79-37-8
3D model (JSmol)	Interactive image
ChemSpider	59021
ECHA InfoCard	100.001.092
EC Number	201-200-2
PubChem CID	65578
RTECS number	KI2950000
UNII	R4Y96317DW
CompTox Dashboard (EPA)	DTXSID3058822
InChI InChI=1S/C2Cl2O2/c3-1(5)2(4)6 Key: CTSLXHKWHWQRSH-UHFFFAOYSA-N InChI=1/C2Cl2O2/c3-1(5)2(4)6 Key: CTSLXHKWHWQRSH-UHFFFAOYAG
SMILES ClC(=O)C(=O)Cl
Properties
Chemical formula	C2O2Cl2
Molar mass	126.93 g/mol
Appearance	Colorless liquid
Density	1.4785 g/mL
Melting point	−16 °C (3 °F; 257 K)
Boiling point	63 to 64 °C (145 to 147 °F; 336 to 337 K) at 1.017 bar
Solubility in water	Reacts
Refractive index (nD)	1.429
Hazards
Main hazards	Toxic, corrosive, lachrymator [2]
Safety data sheet	External MSDS
GHS pictograms	[2]
GHS Signal word	Danger[2]
GHS hazard statements	H314, H331[2]
GHS precautionary statements	P261, P280, P305+351+338, P310[2]
NFPA 704 (fire diamond)	1 3 2 W
Related compounds
Related acyl chlorides	Malonyl chloride Succinyl chloride phosgene
Related compounds	Oxalic acid Diethyl oxalate Oxamide Oxalyl hydrazide Cuprizon 1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Preparation

Oxalyl chloride was first prepared in 1892 by the French chemist Adrien Fauconnier, who reacted diethyl oxalate with phosphorus pentachloride.[4] It can also be prepared by treating oxalic acid with phosphorus pentachloride.[5]

Oxalyl chloride is produced commercially from ethylene carbonate. Photochlorination gives the tetrachloride, which is subsequently degraded:[6]

C₂H₄O₂CO + 4 Cl₂ → C₂Cl₄O₂CO + 4 HCl

C₂Cl₄O₂CO → C₂O₂Cl₂ + COCl₂

Reactions

Oxalyl chloride reacts with water giving off gaseous products only: hydrogen chloride (HCl), carbon dioxide (CO₂), and carbon monoxide (CO).

(COCl)
2 + H
2O → 2 HCl + CO
2 + CO

In this, it is quite different from other acyl chlorides which hydrolyze with formation of hydrogen chloride and the original carboxylic acid.

Applications in organic synthesis

Oxidation of alcohols

The solution comprising DMSO and oxalyl chloride, followed by quenching with triethylamine converts alcohols to the corresponding aldehydes and ketones via the process known as the Swern oxidation.[7][8][9]

Synthesis of acyl chlorides

Oxalyl chloride is mainly used together with a N,N-dimethylformamide catalyst in organic synthesis for the preparation of acyl chlorides from the corresponding carboxylic acids. Like thionyl chloride, the reagent degrades into volatile side products in this application, which simplifies workup. One of the minor byproducts from the N,N-dimethylformamide catalyzed reaction is a potent carcinogen, stemming from the N,N-dimethylformamide decomposition.[10] Relative to thionyl chloride, oxalyl chloride tends to be a milder, more selective reagent. It is also more expensive than thionyl chloride so it tends to be used on a smaller scale.

This reaction involves conversion of DMF to the imidoyl chloride derivative (Me₂N=CHCl⁺), akin to the first stage in the Vilsmeier–Haack reaction. The imidoyl chloride is the active chlorinating agent.

Formylation of arenes

Oxalyl chloride reacts with aromatic compounds in the presence of aluminium chloride to give the corresponding acyl chloride in a process known as a Friedel-Crafts acylation.[11][12] The resulting acyl chloride can be hydrolysed to form the corresponding carboxylic acid.

Preparation of oxalate diesters

Like other acyl chlorides, oxalyl chloride reacts with alcohols to give esters:

2 RCH
2OH + (COCl)
2 → RCH
2OC(O)C(O)OCH
2R + 2 HCl

Typically, such reactions are conducted in the presence of a base such as pyridine. The diester derived from phenol, phenyl oxalate ester, is Cyalume, the active ingredient in glow sticks.

Other

Oxalyl chloride was reportedly used in the first synthesis of dioxane tetraketone (C₄O₆), an oxide of carbon.[13]

Precautions

In March 2000, a Malaysia Airlines Airbus A330-300 was damaged beyond repair after a cargo of prohibited oxalyl chloride (falsely declared as hydroxyquinoline) leaked into the cargo bay.[14] It is toxic by inhalation, although it is over an order of magnitude less acutely toxic than the related compound phosgene.[15]

See also

• Oxalyl

References

1. Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 797. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
2. Oxalyl chloride MSDS
3. Salmon, R. (2001). "Oxalyl Chloride". Encyclopedia of Reagents for Organic Synthesis, 8 Volume Set. Encyclopedia of Reagents for Organic Synthesis. New York: John Wiley & Sons. doi:10.1002/047084289X.ro015. ISBN 0471936235.
4. Fauconnier, Adrien (1892). "Action du perchlorure de phosphore sur l'oxalate d'éthyle" [The action of phosphorus pentachloride on diethyl oxalate]. Comptes rendus hebdomadaires des séances de l'Académie des Sciences (in French). 114: 122–123.
5. DE patent 2840435, Vogel, A.; Steffan, G.; Mannes, K.; Trescher, V., "Process for the preparation of oxalyl chloride", issued 1980-03-27, assigned to Bayer
6. Pfoertner, Karl-Heinz (2000). "Photochemistry". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a19_573.
7. Dondoni, A.; Perrone, D. (2004). "Synthesis of 1,1-Dimethyl Ethyl-(S)-4-formyl-2,2-dimethyl-3-oxazolidinecarboxylate by Oxidation of the Alcohol". Organic Syntheses.; Collective Volume, 10, p. 320
8. Bishop, R. (1998). "9-Thiabicyclo[3.3.1]nonane-2,6-dione". Organic Syntheses.; Collective Volume, 9, p. 692
9. Leopold, E. J. (1990). "Selective hydroboration of a 1,3,7-triene: Homogeraniol". Organic Syntheses.; Collective Volume, 7, p. 258
10. Clayden, Jonathan (2005). Organic chemistry (Reprinted(with corrections) ed.). Oxford [u.a.]: Oxford Univ. Press. pp. 296. ISBN 978-0-19-850346-0.
11. Neubert, M. E.; Fishel, D. L. (1983). "Preparation of 4-Alkyl- and 4-Halobenzoyl Chlorides: 4-Pentylbenzoyl Chloride". Organic Syntheses. 61: 8.; Collective Volume, 7, p. 420
12. Sokol, P. E. (1964). "Mesitoic Acid". Organic Syntheses. 44: 69.; Collective Volume, 5, p. 706
13. Strazzolini, P.; Gambi, A.; Giumanini, A. G.; Vancik, H. (1998). "The reaction between ethanedioyl (oxalyl) dihalides and Ag₂C₂O₄: a route to Staudinger's elusive ethanedioic (oxalic) acid anhydride". Journal of the Chemical Society, Perkin Transactions 1. 1998 (16): 2553–2558. doi:10.1039/a803430c.
14. "Firm told to pay $65 mln for ruining plane". Reuters. 2007-12-06. Retrieved 2007-12-06.
15. Barbee, S.J.; Stone, J.J.; Hilaski, R.J. (January 1995). "Acute Inhalation Toxicology of Oxalyl Chloride". American Industrial Hygiene Association Journal. 56 (1): 74–76. doi:10.1080/15428119591017358. ISSN 0002-8894.